It has been well established that the types and amount of experience available to developing animals has significant effects on the subsequent structure and function of the brain. The proposed experiments examine the effects of environmental stimulation on the growth and development of the olfactory bulbs, a neural region which has been little studied by students of plasticity but is perhaps the most clearly understood and accessible cortical region of the brain. By examining the modifiabilty of the bulb, a model system for subsequent assessments of neural growth and plasticity may be obtained. Specifically, the proposed experiments investigate: 1) the development of odor-specificity in bulbar functioning and the effects of environmental stimulation on its formation and maintenance, 2) the neural effects of rearing rats in environments dominated by a single odor, as an olfactory analogy of the stripe rearing studies of vision researchers, and 3) the consequences of unilaterally blocking stimulation to one bulb on neural development, a manipulation similar to that of monocular deprivation. Moreover, the research addresses several currently popular theories in neurobiology, including 1) hypotheses as to whether experience acts to promote neural growth or only selectively preserves pre-existing strucures while non-stimulated areas regress and 2) the existence of periods of particular susceptibility during early life. By studying the effects of agents which alter the brain during young life, we may come to understand both the normal and pathological development of the brain, and how the environment becomes so crucial during early life.